Polyolefin such as polyethylene (PE), polypropylene (PP) etc. are characterized by not only being lightweight and inexpensive but also having excellent physical properties and processability, but high performance represented by printability, coating ability, heat resistance, impact resistance and compatibility with other polar polymers cannot be realized due to the high chemical stability of polyolefin. For compensating for this disadvantage and endowing the polyolefin with above-mentioned functions, a method of copolymerizing an olefin with a polar monomer such as vinyl acetate or methacrylate by radical polymerization and a method of grafting a polar monomer such as maleic anhydride onto polyolefin in the presence of a peroxide are known. In these methods, however, the structure of a polyolefin moiety in the resulting polymer is hardly accurately regulated, thus making it insufficient to maintain excellent physical properties inherent in the polyolefin.
A means of producing a polymer having a polyolefin in moiety whose structure is accurately regulated and having functions not exhibited by polyolefin only, there can be anticipated a method wherein a polyolefin macromonomer having a polymerizable vinyl bond at the terminal thereof is homopolymerized or copolymerized with various vinyl monomers having functional groups thereby converting the monomer into a graft polymer having polyolefin side chains. As the method of producing a polyolefin macromonomer to synthesize a graft polymer, for example, JP-A 6-329720 describes a method wherein a polymerizable acryloyl or methacryloyl group is introduced into the terminal of polyethylene synthesized by living polymerization. JP-A 8-176354 and JP-A 8-176415 disclose a method of introducing a polymerizable styryl group into the terminal of a polypropylene polymer synthesized by living polymerization. According to a method described in J. Polym. Sci., Part A, 40, 2736 (2002), a polyethylene macromonomer having a methacryloyl group at a polymerization initiation terminal is obtained by living polymerization with a Ni catalyst into which a methacryloyl group was introduced.
In the methods using living polymerization, only one polymer is obtained from one active site on catalyst, and the molecular weight distribution (Mw/Mn) of polyolefin is about 1. However, it goes without saying that the number of polymers obtained from one active site on catalyst is preferably higher from productive viewpoint, and also that the molecular weight distribution (Mw/Mn) of polyolefin is greater for moldability of the polymer. Accordingly, the method utilizing the living polymerization is inadequate, in general, for industrial mass production of polyolefins from economical viewpoint. Further, the method described in JP-A 6-329720 supra makes use of anion polymerization using alkyl lithium, and thus polyolefin producible as a macromonomer is polyethylene with a relatively low molecular weight, that is, a 1000-mer at the maximum, and the method described in JP-A 8-176354 supra makes use of a vanadium compound having a specific structure as an olefin polymerization catalyst, and thus the type of producible polyolefin is limited to a polypropylene polymer.
Further, Polym. Prepr., 33, 170 (1992) discloses a method wherein a low molecular weight polypropylene obtained by a metallocene catalyst is used as a macromonomer, but the number-average molecular weight (Mn) of polypropylene used is as low as 800 to 1000, and from the viewpoint of production of a novel graft polymer having excellent physical properties as polyolefin as one object of the present invention, the macromonomer described in this prior art literature is insufficient for exhibiting excellent property of polypropylene segment, that is, high crystallizability, high rigidity and high heat resistance.
Under these circumstances, the present inventors made extensive examination to develop a polyolefin macromonomer excellent in productivity, consisting of various α-olefin homopolymers or copolymers and capable of covering a broad molecular weight range, and as a result, they found that polyolefin in having a hydroxyl group introduced into the terminal thereof is produced by a coordination polymerization catalyst containing a transition metal compound represented by a solid-state titanium catalyst or a metallocene catalyst used widely in industry as a catalyst for production of polyolefin, and by a method of converting the hydroxyl group into an acryloyl group, a methacryloyl group or a styryl group or by polymerizing a polyolefin macromonomer obtained by such a method, a novel graft polymer useful in various uses can be obtained, thus arriving at the present invention.